Auto-save in VIM as you type

This will handle read-only buffers (like netrw) and undetected filetypes. Using TextChangedI instead of InsertLeave seems to cause a write for every character typed in insert mode, which may or may not be what you want.

augroup autosave
    autocmd!
    autocmd BufRead * if &filetype == "" | setlocal ft=text | endif
    autocmd FileType * autocmd TextChanged,InsertLeave <buffer> if &readonly == 0 | silent write | endif
augroup END

You can use AutoSave plugin to perform that:

https://github.com/907th/vim-auto-save

Please notice that AutoSave is disabled by default, run :AutoSaveToggle to enable/disable it.

I recommend to save the buffer whenever text is changed:

autocmd TextChanged,TextChangedI <buffer> silent write

I found it here. It works for me.

Note (thanks to @Kevin): Unfortunately, it will result in errors if you open vim without opening a file because vim will try to save the text you type but won't have where.